In the prior art known to us, fuel cells have been formed in which the same electrodes are utilized both during charging and discharging of the cell. Fuel cells generally consist of a capillary type electrolyte retaining matrix material sandwiched between two microporous electrodes. These structures permit the establishment of a triple phase interface with a gaseous fuel and an electrolyte in a catalytic electrode pore wherein chemiabsorption takes place. The electrolyte retaining matrix provides a media for ion exchange to the counter electrode of the cell where electron transfer takes place and the electron is dissipated through an external circuit.
In the secondary or rechargeable fuel cell system, an additional reaction takes place upon recharge, namely, fuel generation. This reaction is the reverse of the reaction described above. Fuel and an oxidizing ion are generated at a catalytic electrode cite and an electrolyte ion-exchange then takes place. The oxidizing ion is then neutralized releasing fuel and an electron transfers to the external circuit.
These prior art secondary fuel cell systems are subject to frequent failure. The fuel cell system is limited in cycle life because the anodic electrode during recharge is subject to drying and catastrophic degradation.
It is an object of this present invention to provide a secondary rechargeable fuel cell system which may be charged and recharged over a prolonged lifetime.
It is still another object of this invention to provide a fuel cell system in which each electrode zone has a pair of electrodes, one being more efficient in charging and the other being more efficient in discharge cycle of the system.
The following U.S. patents were cited in a novelty study conducted on the subject matter of this invention disclosure: U.S. Pat. Nos. 3,364,071; 3,382,105; 3,471,336; 3,481,737; 3,554,909; 3,681,145; 3,719,529; 3,769,090; 3,855,002; and 3,905,832. None of the above cited patents show a structure in which pairs of electrodes are used in a fuel cell, one electrode being more efficient in charging of the cell and the other being more efficient during discharge of the cell.